UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS. 


COLLEGE  OF  AGRICULTURE. 

AGRICULTURAL  EXPERIMENT  STATION. 


ARSENICAL  INSECTICIDES 

PAEIS  GREEN;  COMMERCIAL  SUBSTITUTES; 
HOME-MADE  ARSENICALS. 

By  GEO.  E.  COLBY. 


APPLE  LEAF  "BURNED"  BY  PARIS  GREEN. 

BULLETIN  No.  151. 

UNTV  i'OFCAV 

(Berkeley,  May,  1903.)  i  inn  Any 

COLLEGE  OF  AGRiCULT 

SACRAMENTO:  DAV1S 

TV.    W.    SHANNON,      I      I      I      I      I     SUPERINTENDENT    STATE  PRINTING. 

1903. 


BENJAMIN  IDE  WHEELER,  Ph.D.,  LL.D.,  President  0}  the  University. 

EXPERIMENT  STATION  STAFF. 

E.  W.  HILGARD,  Ph.D.,  LL.D.,  Director  and  Chemist. 

E.  J.  WICKSON,  M.A.,  Horticulturist,  and  Superintendent  of  Central  Station  Grounds. 

W.  A.  SETCHELL,  Ph.D.,  Botanist. 

ELWOOD  MEAD,  M.S.,  C.E.,  Irrigation  Engineer. 

R.  H.  LOUGHRIDGE,  Ph.D.,  Agricultural  Geologist  and  Soil  Physicist.    (Soils  and  Alkali.) 

C.  W.  WOODWORTH,  M.S.,  Entomoldgist. 

M.  E.  JAFFA,  M.S.,  Assistant  Chemist.    (Foods,  Fertilizers.) 

G.  W.  SHAW,  M.A.,  Ph.D.,  Assistant  Chemist.    (Soils,  Beet-Sugar.) 

GEORGE  E.  COLBY,  M.S.,  Assistant  Chemist.    (Fruits,  Waters,  Insecticides.) 

RALPH  E.  SMITH,  B.S.,  Plant  Pathologist. 

A.  R.  WARD,  B.S.A.,  D.V.M.,  Veterinarian,  Bacteriologist. 

E.  H.  TWIGHT,  B.Sc,  Diplome  E.A.M.,  Viticulturist. 

E.  W.  MAJOR,  B.Agr.,  Dairy  Husbandry. 

A.  V.  STUBENRAUCH,  M.S.,  Assistant  Horticulturist  and  Superintendent  of  Substations. 

WARREN  T.  CLARKE,  B.S.,  Assistant  Field  Entotnologist. 

H.  J.  QUAYLE,  B.S.,  Assistant  Entomologist. 

H.  M.  HALL,  M.S.,  Assistant  Botanist. 

GEORGE  ROBERTS,  M.S.,  Assistant  Chemist,  in  charge  Fertilizer  Control. 

C.  A.  TRIEBEL,  Ph.G.,  Student  Assistant  in  Agricultural  Laboratory. 

C.  A.  COLMORE,  B.S.,  Clerk  to  the  Director. 


EMIL  KELLNER,  Foreman  of  Central  Station  Grounds. 

JOHN  TUOHY,  Patron,  ) 

V  Tulare  Substation,  Tulare. 
JULIUS  FORRER,  Foreman,  ) 

R.  C.  RUST,  Patron,  ) 

y  Foothill  Substation,  Jackson. 
JOHN  H.  BARBER,  Foreman,  ) 

S.  D.  MERK,  Patron,  ) 

y  Coast  Range  Substation,  Paso  Robles. 
J.  H.  OOLEY,  Workman  in  charge,  ) 

S.  N.  ANDROUS,  Patron,  )  (  Pomona. 

>  Southern   California  Substation,   < 
J.  W.  MILLS,  Foreman,      )  (  Ontario. 

V.  C.  RICHARDS,  Patron, 


Forestry  Station,  Chico. 
T.  L.  BOHLENDER,  in  charge,  ) 

ROY  JONES,  Patron,      ) 

y  Forestry  Station,  Santa  Monica. 
WM.  SHUTT,  Foreman,  ) 


The  Station  publications  (Reports  and  Bulletins)  will  be  sent  to  any 
citizen  of  the  State  on  application,  so  long  as  available. 


ARSENICAL  INSECTICIDES. 


At  the  present  time  there  are  used  in  the  United  States  for  horti- 
cultural purposes  from  1,500  to  2,000  tons  of  paris  green  annually,  and 
the  enormous  increase  in  the  demand  has  caused  manufacturers  to  put 
upon  the  market  products  which  have  been  carelessly  or  hastily  manu- 
factured. 

"White  arsenic"  is  used  in  the  manufacture  of  paris  green,  and  it  is 
not  an  uncommon  practice  to  use  needless  and  excessive  amounts; 
while  on  the  other  hand  the  finished  product  is  often  lower  in  total 
arsenic  than  is  lawful  in  the  State  where  made,  and  then  is  strengthened 
by  the  addition  of  more  "white  arsenic"  (arsenious  oxid).  Thus,  paris 
green,  which  at  best  is  a  somewhat  variable  compound,  comes  by  these 
abuses  to  contain  much  free  arsenious  oxid,  which  in  spraying  materials 
is  ready  and  certain  to  injure  and  destroy  foliage. 

The  application  of  compounds  carrying  any  water-soluble  leaf- 
destroying  matter  is  particularly  dangerous  in  semi-arid  climates. 
Horticulturists  in  California  have  learned  from  experience  that  arsenical 
spraying  materials  are  often  unreliable  and  dangerous,  and  for  years 
have  been  sending  samples  of  their  purchases  of  paris  green  to  this 
Station  for  examination  as  to  purity,  there  being  no  simple  and  easy 
chemical  test  by  which  one  who  is  not  a  chemist  can  satisfactorily 
determine  the  presence  of  "white  arsenic"  in  a  material.  Inasmuch  as 
the  State  of  California  ha~  by  law  fixed  the  maximum  quantity  of 
"white  arsenic"  in  paris  green  for  insecticide  purposes  at  four  per  cent, 
and  requires  an  analysis  to  be  made  by  this  Station  and  a  certificate 
thereof  given  to  the  importer  or  dealer,  it  rests  wholly  with  the 
orchardist  whether  he  uses  safe  material  or  not  on  his  fruit  trees. 
When  buying  paris  green  the  farmer  may  now  demand  to  be  shown  a 
copy  of  the  certificate  before  purchasing;  and  he  may  even  have  the 
particular  parcel  which  constitutes  his  purchase  examined  by  sending 
a  fair  sample  to  the  Station  in  Berkeley. 

Pure  Paris  Green,  also  called  Emerald  green,  Schweinfurt  green  in 
Europe,  is  an  aceto-arsenite  of  copper,  and  may  be  regarded  as  a  com- 
pound of  verdigris  and  ScheeWs  green  (arsenite  of  copper),  having  this 
percentage  composition:  Copper  oxid  (CuO),  31.29;  Arsenious  oxid 
(As,03),  58.65;  and  Acetic  acid  (C,H402),  10.06  (Report  of  N.  J.  Agricul- 
tural Experiment  Station,  1897,  p.  408);  in  other  words,  it  is  a  com- 
pound made  by  the  union  of  three  substances — copper  oxid,  arsenious 
oxid,  and  a  little  acetic  acid.  Ordinary  commercial  paris  green  contains, 
besides  a  very  little  moisture,  some  sodium  sulfate  or  glauber  salt. 
This  salt  usually  occurs  to  the  extent  of  1  or  2  per  cent,  because  it  has 
not  been  fully  washed  out  in  the  process  of  manufacture.  In  the  tables 
of  analyses  of  paris  green,  given  farther  along,  we  have  reported  the 

62352 


4  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

usual  amount  by  the  word  "  small,"  and  excessive  quantities  by  the 
word  "large,"  under  the  head  of  sodium  sulfate.  This  compound  is  of 
no  value  as  an  insecticide:  it  must  be  classed  as  a  " make-weight,"  and 
causes  the  buyer  to  pay  a  very  high  price  (ten  times  more  than  its 
value)  for  every  part  of  paris  green  which  it  replaces. 

While  from  this  or  any  ordinary  description  of  pure  paris  green  it 
might  appear  to  be  a  very  simple  matter  to  make  it,  in  reality  its  manu- 
facture is  difficult,  even  when  effected  according  to  the  latest  "instan- 
taneous" process.  Many  chemicals  enter  into  the  process,  which  must 
be  put  together  in  the  right  proportions,  and  at  just  the  right  time; 
requiring,  besides  experience,  various  kinds  of  appliances  and  machinery, 
"striking-tanks,"  crushing,  sifting,  or  bolting  apparatus— all  of  which 
is  quite  beyond  the  reach  of  any  one  individual. 

Physical  Condition  of  Paris  Green. — The  best  paris  green  is  a  powder 
composed  of  crystalline  globules  of  microscopic  fineness;  and  unless  the 
particles  are  fine  enough  to  pass  through  at  least  a  100-mesh  sieve  the 
green  should  be  condemned  as  unfit  for  spraying  purposes;  for  with  a 
green  in  which  larger  particles  appear  there  is  no  chance  for  an  even 
distribution  of  the  poison.  The  aggregation  of  globules  is  probably 
brought  about  by  careless  grinding  and  bolting,  or  perhaps  by  the  after- 
treatment  with  water  given  to  take  away  impurities.  In  drying  from 
this  operation  the  globules  cohere  and  form  strings  and  bunches  of  par- 
ticles of  green,  which  are  sometimes  found  also  to  be  bound  together  by 
large  lustrous  crystals  of  uncombined  "white  arsenic."  This  latter 
condition  is,  of  course,  very  objectionable,  but  easy  to  determine. 

But  whatever  property  paris  green  possesses,  one  essential  quality  of 
the  pure  article,  in  so  far  as  the  intent  and  purposes  of  spraying  opera- 
tions are  concerned,  is  that  all  of  the  arsenic  in  it  must  be  combined 
with  copper  so  that  it  may  be  insoluble  in  pure  water.  This  is  true,  no 
matter  what  may  be  claimed  by  some  chemists  as  to  its  solubility,  for 
conditions  in  the  laboratory  are  variable  and  do  not  obtain  in  the 
practical  use  of  paris  green  in  the  field. 

WORK    ON    PARIS   GREEN    AT   THIS   STATION. 

The  following  statement  gives  the  character  of  the  work  done  on  paris 
green  at  this  Station  during  the  years  1899,  1900,  1901,  and  1902: 

Before  the  session  of  the  Legislature  of  1901,  this  Station  examined 
thirty-seven  samples  of  paris  green,  and  it  was  found,  and  so  reported, 
that  only  22  per  cent  were  acceptable  for  use  in  California  orchards, 
according  to  its  standard  (p.  17,  Cala.  Stat.  Bull.  126). 

The  results  of  this  work  have  been  useful  not  only  in  establishing  the 
fact  that  manufacturers  can  and  readily  do  produce  paris  greens  that 
will  not  injure  the  leaves  of  the  delicate  peach  or  other  deciduous  trees, 
even  in  the  arid  region,  but  also  in  the  introduction  of  a  more  improved 
and  rational  method  of  analysis,  which  has  been  accepted  by  the 
chemists  of  the  States  whose  results  had  previously  very  frequently 
contradicted  ours.  As  early  as  the  spraying  season  of  1901,  a  number 
of  the  largest  manufacturers  began  to  make  a  paris  green  marked  by  a 


ARSENICAL    INSECTICIDES.  5 

separate  "poster"  on  each  package  as  "paris  green  specially  prepared 
to  conform  to  the  requirements  of  the  Agricultural  Experiment  Station 
of  California,  as  suggested  in  their  Bulletin  No.  126."  These  brands 
were,  on  examination,  found  to  conform  to  the  California  standard;  and 
before  the  spraying  season  of  1902  some  manufacturers  were  offering  to 
the  horticulturists  of  other  States  materials  that  had  been  sent  to  this 
Station  for  judgment  as  to  their  purity. 

At  the  session  (1901)  of  the  Legislature  a  law  was  passed  which  fixed 
the  maximum  permissible  content  of  free  arsenious  oxid  ("white 
arsenic")  at  four  (4)  per  cent,  and  the  minimum  of  total  arsenious 
oxid  in  paris  green  at  fifty  (50)  per  cent.  This  was  the  first  law  in  the 
United  States  which  fixed  the  maximum  quantity  of  " white  arsenic" 
permissible  in  paris  green;  other  State  laws  simply  governed  the  total 
amount  of  the  poison.  In  pursuance  of  this  law  samples  representing 
19  tons  (of  2,000  pounds  each)  have  been  experted,  and  only  five  tons 
(about  26  per  cent)  have  been  condemned  by  not  having  a  certificate  of 
purity  issued  from  this  office  according  to  the  provision  of  the  law. 

Twenty-five  tons  is  about  the  normal  quantity  of  paris  green  used  on  the 
Pacific  Coast,  and  of  this  amount  California  must  have  had  its  fair  share 
last  year,  for  in  addition  to  the  19  tons  examined  there  was  much  in  stock 
whose  weight  was  not  given  by  some  dealers  who  had  failed  to  receive 
a  certificate.  Besides  those  from  the  dealers  or  jobbers,  about  fifty  other 
samples  from  individual  horticulturists  have  been  examined. 

The  paris  greens  in  the  tables  which  follow  are  classified  in  two 
groups,  viz.:  (1st)  Those  examined  here  before  the  California  law 
governing  the  sale  of  paris  green  went  into  effect;  (2d)  Those  exam- 
ined after  the  law  went  into  effect.  Both  these  groups  are,  for  the 
ease  of  determining  the  quality  of  the  articles,  again  subdivided  into 
satisfactory  and  objectionable  articles. 

In  the  first  group  only  one  fifth  were  satisfactory  in  composition,  and 
only  two  out  of  eight  were  received  from  orchardists.  Of  the  objection- 
able articles  of  this  class  or  group  over  one  half  (sixteen  out  of  twenty 
nine)  were  received  from  farmers,  the  rest  coming  from  dealers. 

In  the  second  group,  or  those  received  since  the  law  took  effect,  forty- 
six  were  satisfactory  and  forty-five  were  objectionable.  Of  the  satisfac- 
tory ones  one  half  came  from  the  dealers  and  the  remainder  from  the 
orchardists,  but  some  of  those  from  the  dealers  are  described  as  being 
"only  advance  samples"  for  examination  from  lots  ordered  or  about  to 
be  ordered  from  Eastern  makers. 

Of  the  objectionable  ones  of  the  second  group,  fifteen  out  of  forty-five 
are  from  the  dealers;  private  parties  having,  according  to  their  state- 
ments, sent  in  "left-over"  greens  which  they  wished  analyzed  after 
having  learned  that  a  law  had  been  enacted.  In  any  event,  it  is  seen 
that  the  satisfactory  samples  just  equal  in  number  the  objectionable 
ones  of  this  group.  So  on  the  whole  it  appears  that  the  orchardists 
were  immediately  benefited  by  the  enactment  of  the  paris-green  law. 
Most  of  the  dealers  have  assisted  to  hasten  this  right  condition  of  the 
market  as  regards  the  quality  of  the  material  which  they  have  handled. 


UNIVERSITY   OF   CALIFORNIA — EXPERIMENT    STATION. 


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12  UNIVERSITY    OF   CALIFORNIA EXPERIMENT    STATION. 

PHYSICAL  AND  CHEMICAL  EXAMINATION. 

There  are  no  simple  tests  which  will  enable  a  person  to  quickly  deter- 
mine absolutely  the  purity  of  any  given  sample  of  paris  green.  A 
great  many  forms  of  adulterants,  however,  can  be  immediately  detected. 
Samples  showing  any  considerable  variation  in  color,  especially  an 
abnormally  pale  shade,  is  an  almost  certain  indication  of  adulteration, 
and  those  showing  a  tendency  to  dampness,  or  caking,  should  be 
rejected. 

MICROSCOPIC    EXAMINATION. 

By  far  the  most  satisfactory  of  all  the  easy  methods  for  the  testing  of 
paris  green  is  the  use  of  the  microscope.  For  this  purpose  the  sample  is 
placed  on  a  slip  of  glass,  inclined  and  tapped  gently  so  as  to  leave  only  a 
thin  streak  of  green;  the  glass  slip  is  then  put  under  the  microscope 
and  examined  with  a  medium-power  objective,  about  one  fifth  inch. 
If  the  paris  green  is  pure  it  may  have  several  forms.  If  it  is  of  old 
make,  i.  e.,  five  or  six  years  old,  manufactured  by  slow  process,  it 
appears  as  large,  sharply  defined  spheres  (Plate  I),  with  only  now  and 
then  a  projecting  crystal  of  "  white  arsenic";  if  made  recently  by  the 
rapid  process,  it  appears  in  the  form  of  irregular,  sharp  particles  (Plate 
II, a  and  6),  either  large  or  small.  Sometimes  the  particles  are  separate, 
sometimes  adhering,  but  in  both  kinds  the  projecting  crystals  are  few  in 
number  and  not  often  large.  There  may  also  appear  occasionally  a 
loose  octahedron  of  "white  arsenic"  mixed  in  what  is  called  "broken- 
down"  paris  green.  This  latter  is  simply  slivered  material  from  the 
large  globules,  and  is  the  result  of  over-crushing  of  the  material  when 
reducing  it  to  a  powder;  if  the  focus  of  the  microscope  is  changed  a 
little,  the  real  green  color  of  these  will  appear. 

In  impure  samples  of  paris  green  there  will  be  observed,  in  addition 
to  the  above-described  particles  of  either  spherical  or  irregular  shape,  a 
considerable  quantity  of  material  of  crystalline  shape,  usually  of  white 
color,  the  pure  green  being  quite  distinct  from  the  adulterants  as  seen 
under  the  microscope,  and  as  easily  recognized  as  wheat  can  be  dis- 
tinguished from  impurities  that  might  be  mixed  with  it.    (Plate  III.) 

There  is  more  difficulty  in  distinguishing  paris  green  containing  an 
excess  of  free  "white  arsenic."  This  sometimes  is  added  in  the  form 
of  a  powder,  and  is  then  as  easily  recognized  as  any  other  form  of 
adulterant;  but  when  added  or  retained  in  the  process  of  manufacture 
it  is  firmly  attached  to  the  particles  of  paris  green,  and  only  produces 
the  effect  of  making  them  somewhat  irregular,  and  causing  a  tendency 
toward  sticking  together  (Plate  IV);  the  grade  of  the  material  may 
vary  greatly  and  can  only  be  properly  determined  by  chemical  tests. 

In  the  actual  determination  of  "white  arsenic"  described  in  the  fol- 
lowing pages,  the  process  consists  simply  of  washing  out  the  uncombined 


ARSENICAL    INSECTICIDES. 


13 


arsenious  oxid;  Plate  V,  a,  shows  a  sample  as  it  appeared  before  washing, 
and  Plate  V,  6,  is  the  same  after  being  washed  only  twenty-four  hours. 


Inasmuch  as  some  large  New  York   manufacturers  have  sent  out 
circulars  for   the   purpose   of    trying   to   explain   away   the   value   of 


14 


UNIVERSITY    OF   CALIFORNIA — EXPERIMENT   STATION. 


the  microscopic  test  of  paris  green,   it  is  well   to   repeat  our  opinion 
of  it.     The   test  furnishes  conclusive  evidence  of  the  presence  of  "white 


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ARSENICAL    INSECTICIDES.  15 

crystals  that  the  latter  can  not  be  distinguished  by  this  valuable  and 
ever-ready  test.  These  crystals  are  not  to  be  confused  with  those  of 
"  broken-down "  paris  green  produced  by  "scraping"  and  poor  "bolting," 
as  explained  by  the  manufacturer.  Because  by  these  means  the  crystals 
are  "whitened"  or  deprived  of  color,  as  in  the  case  of  grinding  up  copper 
sulfate,  is  no  reason  to  expect  or  to  imagine  that  they  are  ever  converted 
into  the  shape  of  octahedrons,  or  remnants  of  these,  or  that  they  can  be 
changed  into  anything  which  with  careful  observation  can  be  mistaken 
for  "white  arsenic"  crystals. 

FREE    ARSENIOUS    OXID    IN    PARIS   GREEN. 

The  amount  of  water-soluble  arsenious  oxid  ("white  arsenic")  found 
in  fifty  samples  of  satisfactory  paris  green  during  1900-1902  varies  from 
1.69  to  4.09  per  cent,  with  an  average  of  2.84;  in  the  other  or  objection- 


PLATE  III.    Adulterated  Paris  Green. 

able  class,  comprising  fifty-four  samples,  this  ingredient  ranges  from 
4.70  to  29.40  per  cent.  At  the  New  York  Experiment  Station  (New 
York  is  the  State  in  which  paris  green  is  manufactured)  no  objection- 
able ones  have  been  reported  and  the  content  of  "  white  arsenic"  averaged 
for  the  year  1901  and  1902,  respectively,  1.28  and  1.01  per  cent  in  about 
the  same  number  of  samples  that  were  examined  here,  and  by  practically 
the  same  method  of  analysis  that  we  have  adopted.  Out  of  the  forty- 
five  samples  examined  during  1900  at  the  Bureau  of  Chemistry,  Wash- 
ington, D.  C,  it  was  found  that  according  to  the  four  per  cent  standard 
only  thirteen  specimens  were  passable,  71  per  cent  being  found  objection- 


16 


UNIVEKSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 


able.     This  is  a  worse  state  of  affairs  than  was  found  by  this  Station, 
because  the  paris  greens  examined  at  the  Washington  Bureau  of  Chem- 


S  £ 


P-. 
H 


istry  were  obtained  from  many  Eastern  States,  by  the  Division  of  Ento- 
mology, U.  S.  Agricultural  Department,  Washington.     It  appears  that 


ARSENICAL    INSECTICIDES. 


17 


the  farther  away  paris  green  gets  from  its  place  of  manufacture  (New 
York)  the  worse  it   is   as  to  the  content  of  "  white  arsenic/'  the  leaf- 


H       Oh 
<      5 


6b    &"1 
O 


60     B 

a    fc3 


destroying  material.     In  other  words,  the  orchardists  of  New  York  are 
furnished  with  a  good  class  of  the  insecticide,  while  those  of  other  States 
2 — bull.  151 


18  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

have  to  put  up  with  very  much  poorer  grades,  even  when  they  have 
offered  them  the  protection  of  a  law  governing  its  sale. 

Aside  from  the  injurious  effects  upon  trees  from  the  use  of  such  paris 
greens  as  contain  excessive  quantities  of  u  white  arsenic,"  there  is 
another  aspect  of  the  case,  viz.:  the  fraud  connected  with  the  sale  of 
such  material.  For,  if  from  one  tenth  to  one  third  of  the  weight  of  these 
materials  is  made  up  of  free  "  white  arsenic,"  worth  only  one  third  the 
price  of  good,  passable,  satisfactory  paris  green,  it  is  not  difficult  to  see 
that  the  manufacturers  make  large  unearned  gains  upon  ton  lots.  For 
example,  if  a  wholesale  dealer  obtained  $240  a  ton  for  an  article  which 
contains  one  fourth  free  uncombined  arsenious  oxid,  it  is  a  simple  matter 
to  see  that  he  has  an  unearned  gain  of  about  17  per  cent.  By  the  time 
the  consumer — the  farmer — has  his  small  lot  of  such  objectionable  paris 
green  at  25  and  30  cents  a  pound,  it  becomes  a  very  expensive  material 
for  his  purpose,  especially  if  he  takes  the  trouble  to  add  fresh  lime  to  it, 
so  that  he  has  some  surety  that  his  trees  will  not  be  injured.  He  may 
as  well  take  such  well-known  cheap  material  as  london  purple,  which 
he  knows  must  be  mixed  with  lime  to  prevent  injury  to  foliage,  since  it 
is  sold  to  him  as  a  waste  product  of  the  dye-works  and  is,  therefore,  of 
no  very  definite  composition.  One  had  better  take  the  "simples"  of 
arsenite  of  calcium  or  lead  and  make  his  own  perfectly  safe  arsenical  for 
the  codling-moth,  and  thus  save  both  money  and  trees. 

METHOD     OF     DETERMINING    WATER-SOLUBLE    UNCOMBINED     ARSENIOUS     OXID 
OR    "  WHITE     ARSENIC  "     IN     PARIS     GREEN. 

As  there  has  been  some  difference  of  opinion  among  chemists  in  regard 
to  the  solubility  of  arsenious  oxid  in  water,  we  give  below  a  concrete  exam- 
ple of  what  we  mean  by  washing  the  particles  of  paris  green  free  from  the 
projecting  crystals  of  the  oxid  or  "  white  arsenic  "  as  compared  with  a 
treatment  that  has  proven  insufficient;  and  at  the  same  time  give  the 
method  as  adopted  by  this  Station. 

A  large  lot  of  paris  green  had  been  condemned  by  this  Station  as 
containing  more  than  4  per  cent  of  free  arsenious  oxid,  .though  the 
consulting  chemist  of  a  New  York  firm  of  manufacturers  had  reported 
the  presence  of  less  than  3  per  cent.  This  led  to  a  comparison  of 
methods  upon  the  original  condemned  lot,  and  also  an  examination  of 
the  residue  left  after  his  treatment  which  was  sent  by  the  New  York 
chemist  as  being  free  from  the  arsenious  oxid. 

Microscopic  examination  of  the  original  sample:  Projecting  crystals 
of  arsenious  oxid  mostly  small;  free  octahedrons,  few;  u  broken-down  " 
paris  green,  considerable. 

The  chemical  examination  was  made  by  two  methods,  viz.:  by  that 
described  by  a  commercial  chemist  of  New  York  City,  and  by  the  one 
used  in  the  laboratory  of  this  Station. 


ARSENICAL    INSECTICIDES.  19 

The  method  described  by  the  commercial  chemist  may  be  called  the 
" beaker"  method.  The  temperature  during  this  experiment  varied 
from  20°  to  23.5°  C. 

Beaker  Method. — One  gram  of  paris  green,  placed  in  1  liter  of  distilled 
water  for  forty-eight  hours  at  20°  to  23.5°  C,  with  stirring  every  half 
hour  during  working  hours  (eight),  yielded  soluble  arsenious  oxid  to  the 
extent  of  2.7  per  cent,  and  the  paris  green  residue,  under  microscope,  still 
showed  many  remnants  of  projecting,  lustrous  crystals  of  arsenious  oxid. 
One  half  gram  of  the  dried  paris  green  residue  was  thrown  into  the 
500  cc.  of  first  leaching,  and  allowed  to  digest  for  forty-eight  hours 
more,  with  stirring  as  in  first  half  of  the  experiment.  This  showed 
that  more  soluble  arsenious  oxid  was  present,  to  the  extent  of  2.25  percent 
(of  original  substance  used).  A  microscopic  examination  of  this  second 
paris  green  residue  showed  no  projecting  crystals  or  ridges  of  arsenious 
oxid,  nor  loose  octahedrons  of  the  same  ;  apparently,  too,  the  green  had 
not  suffered  any  change  in  texture  or  color.  By  this  extension  treat- 
ment, this  sample,  washed  free  from  all  adhering  arsenic,  is  shown  to 
contain  a  total  of  4.95  per  cent  of  soluble  arsenious  oxid.  This  is  by 
no  means  so  rigorous  as  that  recommended  by  several  Experiment 
Station  chemists,  wherein  the  time  of  treatment  of  one  gram  of  paris 
green  in  1,000  cc.  of  water  lasts  from  seven  to  as  many  as  fourteen  days, 
at  room  temperature,  for  the  complete  extraction  of  soluble  arsenic  com- 
pounds, reported  as  arsenious  oxid. 

An  examination  of  the  New  York  chemist's  residue,  or  insoluble  matter, 
which  he  had  obtained  after  treatment  with  water  for  forty-eight  hours 
in  his  laboratory,  was  then  made.  This  material  under  the  microscope 
showed  projecting  crystals  of  arsenious  oxid,  and  that  many  particles  of 
paris  green  wTere  impaired  in  color,  i.  e.}  yellowish.  One  half  gram 
of  this  working  residue  of  paris  green  placed  in  500  cc.  of  distilled  water 
at  a  temperature  of  20°  to  24°  for  forty-eight  hours,  and  stirred  as  above, 
showed  by  analysis  that  it  contained  1.70  per  cent  of  uncombined  arsen- 
ious oxid,  which  added  to  the  amount  originally  reported  by  him,  2.73 
per  cent,  brings  the  total  free  arsenious  oxid  in  the  original  green  to  4.43 
per  cent.  This  last  residue  under  the  microscope  showed  no  projecting 
crystals  of  white  arsenic,  and  the  particles  of  paris  green  had  again 
assumed  a  green  color. 

Examination  by  this  Station's  Laboratory  Method. — This  takes  into 
account  not  only  the  limits  of  orchard  practice  with  paris  green,  but 
also  reckons  with  the  remarkable  (?)  properties  ascribed  to  paris  green 
by  some  chemists  when  it  is  treated  with  plain  distilled  water;  regard- 
less of  the  fact  that  this  article — aceto-arsenite  of  copper — as  manufac- 
tured to-day,  is  instantaneously  precipitated  from  complex  solutions 
containing  alkali  and  often  excessive  quantities  of  various  acids. 


20  UNIVERSITY   OF   CALIFORNIA — EXPERIMENT    STATION. 

We,  as  customary,  weighed  half  a  gram  of  the  sample  of  paris  green 
into  a  250  cc.  Erlenmeyer  flask  and  to  it  added  100  cc.  of  distilled 
water,  agitating,  by  shaking,  every  few  minutes  throughout  a  working 
period  (eight  hours)  of  a  day,  keeping  the  liquid  at  only  25°  to  30°  C. 
The  next  day,  after  pouring  off  the  clear  liquid,  a  fresh  100  cc.  of 
distilled  water  was  added,  and  all  this  treatment  was  repeated  on  this 
and  the  following  day — in  all  twenty-four  hours.  Finally  the  three 
100  cc.  leachings  were  combined,  filtered  through  a  double  filter,  and 
the  water-soluble  arsenious  oxid  determined.  It  amounted  to  4.75  per 
cent  of  the  original  paris  green.  The  residue  from  this  experiment  did 
not  show  under  the  microscope  any  lustrous  crystals,  either  projecting 
or  loose,  of  arsenious  oxid — and  the  texture  and  color  of  the  globules  of 
green  seemed  unaltered. 

The  three  results  for  free  arsenious  oxid  in  this  paris  green  may  be 
tabulated,  for  convenience,  as  follows  : 

Per  Cent. 

By  method  of  New  York  chemist 2.73  ) 

Treatment  of  same  continued  by  us  .. ._ 2.22) 

Originally  found  by  New  York  chemist - 2.73  ) 

Found  by  us  in  the  residue  sent  by  him 1.70  j 

By  method  of  this  Station _._ _ 4.75 

We  may,  therefore,  safely  conclude  that  the  "  beaker  "  method  of  only 
forty-eight  hours'  exposure  is  insufficient  for  taking  out  all  of  the 
soluble  "  white  arsenic,"  but  an  extension  of  the  time  to  another  forty- 
eight  hours  dissolves  all  this  material  from  paris  green.  The  copper 
dissolved  in  all  of  these  tests  only  amounted  to  0.10  per  cent. 

Many  paris  green  samples  from  New  York  factories,  when  analyzed 
by  this  Station's  laboratory  method,  fall  into  the  "  safe  class,"  i.  e.,  those 
containing  somewhat  less  than  4  per  cent  of  free  arsenic;  and,  to-day, 
we  are  reporting  one  with  only  2.3  per  cent.  All  of  these  tests  have 
been  controlled  and  confirmed  by  the  microscope,  which  proved  that  all 
the  water-soluble  arsenious  oxid  was  removed  by  washing. 

The  above  simple  form  and  description  of  the  working  of  the  method 
adopted  by  this  Station  was  sent  to  the  manufacturer's  chemists  in 
New  York  during  the  summer  of  1901,  and  they  obligated  themselves  to 
distribute  it  among  the  chemists  interested  in  the  manufacture  of  paris 
green,  for  the  obvious  reason  that  they  all  wished  to  be  sure  that  the 
articles  which  they  experted  would  in  every  case  come  within  the  law 
of  California.  Undoubtedly  this  method  was  well  distributed,  for  since 
then  there  has  been  no  correspondence  on  the  subject  with  any  manu- 
facturing chemists. 

Total  Arsenious  Oxid. — In  fifty  samples  in  which  this  determination 
has  been  made,  only  four  yielded  less  than  the  amount  required  by  law> 
i.  e.}  50  per  cent;  and  all  of  these  greens  with  low  total  arsenious  oxid 
appear  in  the  class  of  objectionable  ones   (those  classed  as  containing 


ARSENICAL    INSECTICIDES.  21 

excessive  quantities  of  uncombined  arsenious  oxid).  In  no  case  where 
the  green  is  otherwise  satisfactory,  is  the  total  arsenic  below  the  stand- 
ard; rather,  it  closely  approaches  the  theoretical  amount  in  combination 
with  copper  in  pure  green,  viz.,  58.65  per  cent,  and  often  exceeds  this 
figure.  The  significance  of  this  outcome  would  be  to  establish  the  right 
to  recommend  the  raising  of  the  required  amount  of  total  arsenious 
oxid  in  green  for  horticultural  purposes  several  points,  and  to  be  at  least  55 
or  57  per  cent,  by  statute.  The  total  arsenious  oxid  as  taken  by  other 
Experiment  Station  chemists  during  the  last  year  or  two  has  apparently 
been  raised  by  a  point  or  two;  and  this,  as  observed  by  us  in  samples 
containing  less  than  4  per  cent  water-soluble  "  arsenious  oxid."  All  of 
which  means  that  manufacturers  are  approaching  closely  a  definite  com- 
pound of  copper,  ''arsenic/' and  " vinegar'' — a  thing  so  much  desired 
on  all  sides  when  they  are  improving  the  green  in  respect  to  water- 
soluble  "  white  arsenic/' 

Copper,  as  Copper  Oxid,  in  Paris  Green. — A  few  determinations  of  this 
ingredient  shows  no  great  variation  from  31.29  per  cent  as  given  for 
pure  paris  green;  the  results  obtained  here  are  quite  similar  to  those 
obtained  elsewhere,  and  all  agree  that  ordinary  green  may  contain  from 
26.5  to  as  much  as  32.0  per  cent  of  copper  oxid.  The  quantity  of  copper 
oxid  which  goes  into  solution  in  the  treatment  of  paris  green  with  water 
is  exceedingly  small.  In  the  course  of  twenty-four  hours'  treatment  in 
determining  water-soluble  "white  arsenic"  the  maximum  amount 
found  was  only  0.30  per  cent. 

The  value  and  use  of  these  results  belong  to  the  future,  since  it  is  not 
possible  with  our  present  knowledge  to  make  practical  use  of  the  water- 
soluble  copper  oxid  determination. 

ADULTERATION    OF   PARIS   GREEN. 

This  Station  has  never  yet  analyzed  a  sample  of  paris  green  in  which 
adulterants  were  added  to  the  extent  reported  of  foreign  paint  materials. 
This  is  also  the  experience  of  several  Eastern  experiment  stations.  In 
Germany  the  case  is  quite  different,  for  much  adulterated  green  is  found 
containing  barium  sulfate,  calcium  carbonate,  chrome  yellow,  iron  oxid, 
lead  chromate,  etc.  In  part  these  materials  are  simple  make-weights, 
while  others  are  added  in  order  to  produce  different  desired  tints  of  color. 

Such  materials  as  barium  sulfate,  fine  sand,  calcium  carbonate,  etc., 
are  easily  recognized  by  their  insolubility  in  ammonia,  and  so  we  have 
a  very  easy  way  of  detecting  them  in  paris  green,  which  completely 
dissolves  in  this  liquid,  turning  it  to  an  intense  blue  color. 

This  test,  however,  is  not  conclusive,  since  white  arsenic  and  a  number 
of  other  substances  used  in  adulterating  paris  green,  especially  in  these 
later  years,  are  soluble  in  ammonia  and  would  escape  detection  if  this 


22  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

method  alone  were  depended  on.  Insolubility  of  any  portion  of  it  in 
ammonia,  then,  affords  valid  grounds  for  rejecting  a  sample;  but  other 
means  must  be  used  to  be  sure  of  its  purity,  even  if  apparently  pure  by 
this  test. 

This  is  still  more  emphasized  when  it  was  found  that  many  commer- 
cial chemists  last  year  made  a  common  mistake  in  regard  to  their  inter- 
pretation of  the  result  of  the  ammonia  test  with  paris  green,  viz.:  in 
concluding  that  because  the  material  is  completely  soluble  in  ammonia 
"therefore  it  is  free  from  white  arsenic."  Now,  "white  arsenic"  is  itself 
soluble,  and  at  this  Station  we  have  repeatedly  mixed  various  grades  of 
it  with  paris  green,  even  up  to  equal  proportions  of  these  materials, 
and  treated  them  with  cold  ammonia  in  the  proportion  of  one  to  ten,  and 
have  yet  to  find  a  case  in  which  all  the  "white  arsenic"  failed  to 
dissolve;  and  this  is  accomplished  in  a  few  minutes,  instead  of  taking 
hours  as  announced  by  some.  The  reason  for  this  error  by  commercial 
chemists  is  not  far  to  seek,  when  a  prominent  Eastern  experiment  sta- 
tion chemist  in  a  bulletin  states  most  clearly  that  "  the  insolubility  of 
paris  green  in  strong  ammonia  is  a  fair  test  of  purity,  so  far  as  concerns 
the  addition  of  white  arsenic  and  insoluble  adulterants  like  calcium 
sulfate,  barium  sulfate,  etc.  We  have  indicated  those  samples  that 
dissolve  easily  and  completely  in  strong  ammonia,  making  a  perfectly 
clear  solution  without  sediment.  These  samples  were  free  from  "white 
arsenic." 

One  has  only  to  consult  a  few  authorities  to  find  that  "  white  arsenic" 
is  classed  as  soluble  in  ammonia;  for  instance,  Storer's  Dictionary  of 
Solubilities,  under  "Arsenious  Oxid,"  says,  "  Readily  soluble  in  aqueous 
solution  of  arsenite  of  ammonia  (or  in  caustic  ammonia),"  etc.  Comey's 
Dictionary  of  Chemical  Solubilities,  p.  30,  Arsenious  Oxid — "  Easily  solu- 
ble in  alkali  hydrates,  or  carbonates  plus  water."  U.  S.  Dispensatory, 
17th  edition,  p.  24,  makes  note  of  solution  of  arsenious  oxid  in  ammonia 
as  tests  for  impurities  in  the  white  arsenic.  Wormley's  Micro-chemistry 
of  Poisons,  at  page  256,  reads,  "Arsenious  oxid  is  readily  soluble  in  solu- 
tions of  the  fixed  caustic  alkalies,  but  is  much  less  soluble  in  ammonia." 
Douglass  &  Prescott's  Qual.  Chem.  Anal.,  p.  112,  "Arsenious  anhydride 
is  readily  soluble  in  alkali  hydrates  with  combination."  Graham-Otto, 
Lehrbuch  der  Chemie,  Vol.  3;  p.  472:  "  Kalilauge,  Natronlauge  und 
Ammoniakflussigkeit  losen  die  arsenige  Saure  in  reichlicher  Menge  auf, 
ohne  dass  die  alkalische  Reaction  verschwindet,  damit  Arsenigsaure- 
Salze  bildend  (siehe  diese  unten).  Die  Auflosung  in  Ammoniakflus- 
sigkeit hinerlasst  bein  Verdampfen  arsenige  Saure  (siehe  oben;  ferner 
unten:  arsenigsaures  Amnion.)." 

It  may  generally  be  said  of  paris  green  in  this  market,  so  far  as  the 
samples  examined  here  represent  the  condition,  that  there  is  hardly 
ever  any  practice  of    adding  "make-weights,"  such   as   marble   dust, 


ARSENICAL    INSECTICIDES.  23 

gypsum,  etc.     This  has  also  been  the  experience  of  the  secretary  of  the 
State  Board  of  Horticulture  of  California. 

This  market  is  fast  coming  to  be  in  very  fair  condition  as  to  samples 
which  come  within  the  law,  and  especially  those  containing  less  than  4 
per  cent  of  "white  arsenic";  still  there  is  much  room  for  improvement  as 
compared  with  the  reported  condition  in  this  respect  of  the  paris  greens 
on  sale  in  New  York  State,  where  all  are  satisfactory,  according  to  the 
findings  of  the  Agricultural  Experiment  Station  at  Geneva,  New  York. 

CHARACTER  AND    VALUE  OF    SOME   OF   THE    LATEST  COMMERCIAL  SUBSTITUTES 

FOR   PARIS   GREEN. 

The  extensive  use  of  london  purple  as  a  cheaper  arsenical  insecticide 
than  paris  green,  and  the  widespread  recommendation  of  all  the  ento- 
mologists of  this  country  to  mix  it  and  paris  green  with  an  equal  weight 
of  fresh  lime  for  the  neutralization  of  the  uncombined  arsenic  in  it,  have 
given  the  manufacturers  of  arsenical  insecticides  an  excuse  for  making  and 
offering  for  sale  many  patented  compounds  of  arsenic,  lime,  and  copper; 
of  course  the  many  failures  from  the  use  of  poor  paris  green  also  help 
them  out.  Some  are  imitations  of  paris  green;  often  they  contain 
little,  if  any,  green-colored  arsenite  of  copper,  and  even  lead  arsenite 
has  been  dyed  green  and  sold  as  "  Green  Arsenite."  Now  london  purple, 
Scheele's  green  or  "  green  arsenite,"  and  lead  arsenite,  are,  when  properly 
compounded,  safe  insecticides,  and  equal  to  paris  green  in  value 
against  insects.  What  we  wish  to  show  is  that  the  majority  of  the 
later  and  cheap  commercial  combinations  of  lime,  arsenic,  and  copper 
are  poor  substitutes  for  satisfactory  paris  green,  and  that  they  hardly 
ever  possess  the  chief  property  of  not  containing  leaf-scorching  materials, 
as  is  universally  claimed  for  them.  Also,  that  they  are  heavier  materials 
than  would  appear  from  the  ordinary  commercial  description  of  them. 

Among  these  arsenicals  the  following  have  been  examined  at  this 
Station:  Paragrene,  Laurel  Green,  Calco-Green,  and  the  various  green, 
white,  red,  and  gray  Arsenoids. 

Paragrene. — A  recent  arsenical  spraying  material  is  a  patented  article 
bearing  the  name  "Paragrene,"  samples  of  which  have  been  received 
for  examination  by  this  Station.  The  manufacturers  of  paragrene 
claim  "that  the  article  was  very  extensively  used  last  year  by  planters 
and  growers  all  over  the  country,  and  that  it  is  free  from  the  objection- 
able features  of  paris  green,  in  that  it  does  not  burn  or  scorch  the 
most  tender  foliage.  It  contains  the  required  percentage  of  arsenic  as 
arsenious  oxid.  Besides  this,  the  article  is  considerably  cheaper  than 
paris  green."  It  retails  at  from  13  to  17  as  against  25  or  30  cents  per 
pound  for  paris  green. 

A  microscopic  examination  shows  that  this  material  contains,  besides 


24  UNIVERSITY    OF   CALIFORNIA— EXPERIMENT    STATION. 

the   ordinary   green,   a    considerable   quantity   of  sulfate   of  calcium 
(gypsum)  and  also  many  crystals  of  "white  arsenic." 
The  substance  analyzed  as  follows: 

Per  Cent. 

Copper  oxid  (CuO) 23.46 

Arsenious  oxid  (As203),  combined  ... 17.52 

Arsenious  oxid  (As203),  free 23.08 

Acetic  acid 6.72 

Calcium  sulfate  (gypsum) . 19.31 

Sodium  sulfate 2.26 

Sodium  chlorid 25 

Peroxid  of  iron .. .20 

Water 6.20 

Total 99.00 

Notwithstanding  that  the  above  composition  complies  in  many  par- 
ticulars with  the  claim  made  for  it  in  the  Patent  Office,  the  fact  that  it 
contains  so  much  (nearly  one  fourth  its  weight)  of  free,  water-soluble 
arsenious  oxid  stands  against  it.  In  this  sample  of  paragrene  the  free 
arsenious  oxid  is  as  high  as  in  some  of  the  most  objectionable  paris  greens. 
This  article,  therefore,  must  be  rejected,  as  it  will  positively  cause  injury 
to  foliage  if  used  in  California  orchards. 


Laurel  Green. — Manufactured  by  the  Nichols  Chemical  Company, 
New  York.     Composition: 

Per  Cent. 

Gypsum  (land  plaster) 50.0 

Calcareous  sand  (greensand) 20.2 

Arsenite  of  copper _ 24.7 

Moisture,  etc _ _ 5.1 

Total 100.0 

Soluble  arsenic  compounds .8 

All  such  articles  as  this  analysis  shows  this  laurel  green  to  be  can 
never  be  recommended  for  spraying  purposes,  because  they  do  not  con- 
tain enough  arsenic  to  make  them  effective  when  used  according  to  the 
usual  formulas.  This  material  consists  chiefly  (three  fourths)  of  gyp- 
sum and  greensand,  both  of  which  are  only  in  the  way  in  spraying 
operations.  The  greensand  shows  a  very  poor  attempt  at  plain  fraud. 
No  matter  how  cheap  this  article  is  it  will  not  pay  to  handle  it  for 
fighting  insects. 

Calco-Green. — This  is  offered  as  a  cheap  substitute  for  paris  green, 
the  price  being  9  cents  a  pound.  It  is  a  gray-green  fine  powder  con- 
taining: 

Per  Cent. 

Total  arsenious  oxid ... . 30.0 

Water-soluble  arsenious  oxid 7.0 

This,  besides  being  an  unsafe  material  because  of  its  large  content  of 
soluble  arsenic,  has  too  little  total  arsenic  to  make  it  worthy  of  trial  even 
in  an  experimental  way. 


ARSENICAL    INSECTICIDES.  25 

Gray  Arsenoid  (Calcium  and  Copper  Arsenite)  is  thus  described  by 
the  maker  who  sent  a  sample  to  us  for  examination:  "This  arsenite  of 
copper  and  lime  is  so  prepared  that  it  is  absolutely  free  from  uncombined 
arsenious  oxid  and  has  an  alkaline  reaction.  While  the  percentage  of 
total  arsenious  oxid  (guaranteed  to  be  38.30)  is  not  as  great  as  that  of 
paris  green,  it  has  the  advantage  that  it  can  be  used  in  any  strength  as 
a  spray  without  injury  to  the  foliage.  Being  a  comparatively  inex- 
pensive article  (8  cents  per  pound),  a  greater  strength  of  solution  can 
be  used  at  the  same  cost,  thus  overcoming  the  differences  in  the 
efficiency  that  exist  in  solutions  of  equal  strength.  It  has  the  advan- 
tage of  a  comparatively  very  small  specific  gravity,  which  prevents  it 
from  settling  speedily  in  water;  thus  forming  a  spray  of  uniform 
strength,  which  in  the  case  of  paris  green  involves  considerable 
difficulty." 

Analysis  of  Gray  Arsenoid. 

Per  Cent. 

Moisture 16.10 

Arsenious  oxid  (combined) 21.24 \ 


L.24) 
5.76  J 


Arsenious  oxid  (uncombined),  soluble 13. 

Copperoxid.. 15.10 

Calcium  oxid _ .._• 27.10 

Carbonic  acid,  Prussian  blue,  sodium  sulfate,  etc. 6.70 

Total _ 100.00 

The  result  of  the  examination  of  this  arsenoid  leads  to  an  unfavora- 
ble conclusion,  and  chiefly  on  account  of  the  soluble  arsenic  in  it,  which 
amounts  to  13.74  per  cent.  It  appears  that  this  material  (aside  from 
its  copper  and  absence  of  dye)  resembles  london  purple,  but  may  be  rated 
superior  to  it  because  it  shows  considerably  less  soluble  arsenic.  This 
arsenoid,  like  the  familiar  article  named  above,  when  used,  perhaps 
may  have  the  soluble  arsenic  in  it  corrected  or  neutralized  by  mixing  it 
with  an  equal  weight  of  fresh  lime. 

White  Arsenoid  (Barium  Arsenite). — This  material  upon  analysis 
was  found  to  be  of  the  following  composition  : 

Per  Cent. 

Barium  carbonate.. ._ _ 44.05 

Barium  chlorid.. 13.05 

Barium  oxid 8.18 

Arsenious  oxid,  free _._ .__ 27.64 

Lead  carbonate.. 1.86 

Silica 20 

Moisture _. 4.00 

Total 98.98 

The  only  ingredient  which  might  give  this  compound  a  value  for 
spraying  trees  is  the  arsenious  oxid.  But  all  of  this  oxid  is  in  such  a  con- 
dition that  it  is  extremely  dangerous  to  foliage,  and  practical  tests  have 
shown  it  to  be  so.     Probably  the  other  soluble  barium  compounds  act 


26  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION. 

as  poisons  upon  plants.  Of  the  other  components,  the  largest,  barium 
carbonate,  simply  makes  weight  and  adds  nothing  to  its  value.  The 
same  is  true  of  all  the  other  ingredients.  Notwithstanding  that  this 
material  is  offered  for  a  much  lower  price  than  paris  green,  it  can  not  be 
safely  recommended. 

Green  Arsenoid  (Copper  Arsenite). — This  compound  is  "dead"  green 
in  color,  and  under  the  microscope  is  seen  to  be  a  mass  of  irregular, 
sharp  crystals.  It  shows  the  presence  of  some  soluble  blue*  which  often 
contains  arsenic.     It  analyzes  as  follows  : 

Percent. 

Copper  oxid  (CuO) _ 28.83 

Arsenious  oxid  (As203),  combined _ 53.51)  g.  ,, 

Arsenious  oxid  (As203),  free 7.82' 

Moisture 2.77 

Silica .40 

Organic  matter  derived  from  soluble  blue ;  sulfate  of  soda,  etc 6.67 

Total 100.00 

While  this  material  contains  the  guaranteed  quantity  of  arsenious 
oxid,  and  is  cheaper  than  the  common  green,  still  it  is  hardly  safe,  as  it 
stands,  to  use  in  this  climate,  with  its  nearly  8  per  cent  of  free  arsenious 
oxid. 

Pink  Arsenoid  (Lead  Arsenite). — This  material  is  colored  with  some 
pink-colored  aniline  residue,  and  shows  the  following  composition  by 

analysis: 

Per  Cent. 

Lead  oxid  (PbO) 49.58 

Arsenious  oxid  (As203),  combined 40.02 

Arsenious  oxid  (As203),  free _ _ 3.24 

Moisture .._ _ _ .31 

Organic  matter  from  aniline  residue;  lead  sulfate,  etc. 6.85 

Total 100.00 

This  compound  can  not  be  objected  to,  and  a  practical  test  with  it 
shows  that  it  is  perhaps  but  little,  if  any,  more  dangerous  to  foliage  than 
paris  green.  It  is  sold  for  much  less  than  ordinary  green;  this,  when 
considered  with  the  low  content  of  free  arsenious  oxid,  should  recom- 
mend it. 

Conclusions  Regarding  These  Commercial  Substitutes. — It  appears  from 
the  foregoing  record  that  of  these  "  arsenoids"  the  lead  compound  is  the 
best;  i. e.,  the  least  injurious.  The  copper  compound  is  certainly  prom- 
ising, and  if  proper  methods  are  followed  in  its  manufacture  it  can 
easily  be  made  a  desirable  insecticide.  But  of  the  barium  compound 
nothing  more  need  be  said  than  that  it  is  simply  worthless.  It  is  a 
grave  mistake  to  put  it  on  any  market  for  the  use  for  which  it  was 
intended. 

*Sodium  triphenylrosaniline-monosulphonate. 


ARSENICAL    INSECTICIDES.  27 

The  physical  properties  of  these  commercial  substitutes,  especially 
those  which  determine  and  show  how  long  they  will  remain  in  suspen- 
sion in  water,  have  been  studied  and  the  results  are  given  on  page  34. 

It  will  be  seen  there  that  all  but  one  of  them,  the  pink  arsenoid,  show 
no  more  advantage  in  this  respect  than  london  purple  does  over  finest 
powdered  paris  green.  Briefly,  they  remain  in  suspension  only  twice  as 
long  as  paris  green,  which,  to  say  the  least,  means  that  they  are  not  high- 
grade  materials,  and  therefore  they  are  disappointing  from  this  point  of 
view.  But  of  all  the  cheaper  compounds  of  later  make  offered  to  take  the 
place  of  the  expensive  paris  green,  only  one,  the  pink  arsenoid,  can  be 
with  safety  recommended  to  the  orchardist  as  not  liable  to  burn  his  trees. 

The  conclusion  that  these  articles  do  not  answer  the  purpose  for 
which  they  were  intended  is  quite  in  accordance  with  the  generally 
accepted  one  regarding  all  proprietary  articles,  no  matter  of  what 
description,  offered  as  insecticides  or  fungicides,  viz.:  that  they  seldom 
are  what  they  are  claimed  to  be,  and  often  are  of  little  or  no  value 
against  pests,  or  even  as  fertilizers  if  they  should  happen  to  fall  upon 
the  soil. 

In  view  of  these  facts  the  orchardist  should  consult  some  authority 
before  purchasing  any  article  of  this  kind,  in  order  that  its  composition 
and  qualities  may  become  known  to  him.  This  he  should  first  do  by 
inquiry  of  his  own  Agricultural  Experiment  Station,  in  order  not  only  to 
save  his  cash  in  hand,  but  also  to  increase  the  yield  of  his  orchard  by 
avoiding  the  burning  of  the  leaves  of  the  trees  upon  which  he  is  advised 
by  some  dealer  to  put  such  poor  materials. 


HOME-MADE    ARSENICALS. 
(These  comprise  compounds  of  lead  and  arsenic,  and  of  lime  and  arsenic.) 

There  seems  to  be  no  good  reason  why  these  may  not  be  used  in  all 
places  in  spraying  where  arsenicals  are  employed,  for  they  possess  the 
following  excellent  properties,  viz.:  first,  they  are  easily  made,  and  the 
resulting  compounds  from  the  "simples"  have  the  most  definite  compo- 
sition among  the  arsenicals  used:  second,  it  can  be  shown  that  they  are 
the  cheapest  arsenicals;  third,  that  the  lead  arsenicals  are  the  most 
insoluble  of  all  combinations  of  arsenic  and  metals,  and  therefore  the 
least  liable  to  burn  the  foliage,  no  matter  how  delicate  it  may  be;  fourth, 
these  materials  do  not,  like  paris  green,  require  a  constantly-working 
agitating  machine  in  the  process  of  spraying — a  turn  of  the  machine 
now  and  then  will  be  enough  to  keep  them  in  suspension,  and  therefore 
insure  an  even  distribution  of  the  poison  over  the  whole  orchard; 
fifth,  practical  tests  with  them  show  that  their  action  is  excellent  from 
all  points  of  view. 


28  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 

Lead  Compounds. 

Arsenate  of  Lead. — There  are  two  methods  of  making  this  compound — 
either  by  mixing  the  ordinary  acetate  of  lead  (sugar  of  lead),  or  the 
more  expensive  nitrate  of  lead  with  the  best  quality  of  arsenate  of 
soda.  The  resulting  compounds  are  of  slightly  different  composition, 
but  of  equal  effectiveness  against  insects  in  their  poisoning  properties. 

Since  it  is  an  important  matter  to  know  the  composition  of  the 
ingredients  used  in  the  manufacture  of  arsenate  and  arsenite  of  lead, 
we  give  the  following  information  for  the  guidance  of  the  purchaser: 
The  articles  to  be  used  are  acetate  of  lead  (sugar  of  lead)  and  arsenate 
of  soda.  They  should  be  guaranteed  to  be  first  class,  and,  if  necessary, 
the  purchaser  may  have  their  composition  determined  at  the  Experi- 
ment Station. 

First-class  crystallized  lead  acetate  (sugar  of  lead  )  should  contain 
about  58.8  per  cent  of  available  lead  oxid,  but  it  dries  out  or  loses  some 
water  in  the  air  and  thus  ordinarily  contains  from  60  to  62  per  cent.  It 
is  readily  soluble  in  cold  water  in  the  proportion  of  one  pound  to  one 
gallon  of  water.  In  hot  water  it  readily  dissolves  in  a  less  quantity, 
and  for  its  quick  solution  hot  water  is  always  preferable.  This  is  the 
cheapest  water-soluble  lead  salt  in  commerce,  and  therefore  will 
probably  be  used  most  frequently.  Its  wholesale  price  is  7i  cents  per 
pound. 

Arsenate  of  soda  should  have  not  more  than  2  or  3  per  cent  of  chlorin, 
as  this  changes  the  lead  acetate  into  lead  chlorid,  thus  occasioning 
waste;  lead  chlorid  being  of  no  value  as  an  insecticide.  What  is  known 
as  "  sixty-eight  per  cent "  arsenate  of  soda  contains  about  47.8  per  cent 
of  arsenic  acid  and  only  0.57  per  cent  of  chlorin.  The  remainder  of  the 
material  consists  of  the  normal  materials  entering  into  its  composition; 
i.  e.,  soda,  potash,  water  of  crystallization,  a  trifling  amount  of  sulfate 
of  soda,  and  insoluble  matter.  This  salt  is  very  soluble  in  hot  water, 
which  is  preferable  for  its  solution.  The  wholesale  price  of  arsenate 
of  soda  is  5  cents  per  pound. 

The  formula  for  making  one  pound  of  lead  arsenate,  i.  e.y  enough  for 
from  100  to  150  gallons  of  water,  is  to  dissolve  24  ounces  of  acetate  of  lead 
(or  20  ounces  of  lead  nitrate)  in  one  gallon  of  cold  water;  also  separately 
10  ounces  of  arsenate  of  soda  in  three  quarts  of  water;  both  in  wooden 
vessels.  These  weighed  quantities  can  be  bought  in  separate  parcels 
and  are  superior  to  any  mixture  of  them  which  may  be  offered.  The 
separate  solutions  are  to  be  poured  together  into  the  spray  tank  filled 
with  water.  A  white  precipitate  of  lead  arsenate  ready  for  spraying 
immediately  forms  in  the  tank;  its  fine  flocculent  condition  keeps  it  in 
suspension  for  hours,  and  of  all  arsenicals  it  is  the  most  easily  kept 
suspended  in  water. 


ARSENICAL   INSECTICIDES.  29 

The  above  is  the  ordinary  recommendation;  but  the  preparation  can 
be  used  several  times  stronger  if  desired,  without  the  least  danger  of 
producing  any  injury  to  foliage,  even  if  used  at  the  rate  of  from  3  to 
15  pounds  to  100  gallons  of  water. 

To  prove  conclusively  that  this  spray  liquid  contains  lead  in  excess, 
as  it  should,  one  has  only  to  take  out  a  little  of  it  and  test  it  with  a 
few  drops  of  potassium  bichromate,  when  there  should  be  a  yellow- 
colored  precipitate. 

Lead  arsenate,  made  as  above  directed  from  the  best  quality  of  both 
lead  acetate  and  soda  arsenate,  has  the  following  composition: 

Per  Cent. 

Water -— 2.37 

Leadoxid(PbO) - 73.10 

Arsenic  pentoxid  (As205) .. 21.80 

Chlorin 2.40 

Total 99.67 

In  the  market  there  are  now  found  several  kinds  of  lead  arsenate 
ready  for  use;  sometimes  it  is  a  dry  powder,  white  or  colored  with  a  dye, 
and  sometimes  a  paste  mixed  with  tar  or  glucose  to  make  it  stick  to  foliage 
or  to  attract  insects.  Such  a  compound  as  the  latter  is  "  Swift's  arsenate 
of  lead."  A  sample  of  the  white  dry  powder  variety  was  shown  by 
analysis  here  to  contain  25.90  per  cent  of  arsenic  pentoxid,  68.06  per 
cent  of  lead  oxid,  and  1.16  per  cent  of  chlorin,  the  rest  being  principally 
water.  There  were  present  0.80  per  cent  of  water-soluble  arsenic 
compounds. 

Swift's  arsenate  of  lead,  in  the  form  of  paste,  usually  has  the  following 
composition,  as  shown  by  an  analysis  recently  made  in  this  laboratory: 

Per  Cent. 

Lead  oxid.. _ ...  36  00 

Arsenic  pentoxid 12.00 

Organic  matter  (glucose)  and  other  organic  matter 9.00 

Water 43.00 

Total 100.00 

Water-soluble  arsenic  oxid __. 0.15 

While  both  of  these  have  the  requisite  amount  of  actual  poison 
to  make  them,  in  practice,  sufficiently  strong  when  made  up  with 
the  usual  quantity  of  water,  they  do  not  come  up  to  the  standard  when 
compared  with  freshly  precipitated,  home-made  lead  arsenate,  for  they 
settle  in  the  spray  tank  much  quicker.  Of  course  the  dry  form  settles 
quickest,  but  remains  in  suspension  about  four  times  as  long  as  the 
finest-powdered  paris  green;  while  the  home-made  lead  arsenate  will 
remain  suspended  fourteen  times  as  long. 

"Disparene"  is  the  trade  name  for  a  much-advertised  new  form  of 
arsenate  of  lead,  a  bluish-gray  colored  paste,  which  the  makers — The 


28  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 

Lead  Compounds. 

Arsenate  of  Lead. — There  are  two  methods  of  making  this  compound — 
either  by  mixing  the  ordinary  acetate  of  lead  (sugar  of  lead),  or  the 
more  expensive  nitrate  of  lead  with  the  best  quality  of  arsenate  of 
soda.  The  resulting  compounds  are  of  slightly  different  composition, 
but  of  equal  effectiveness  against  insects  in  their  poisoning  properties. 

Since  it  is  an  important  matter  to  know  the  composition  of  the 
ingredients  used  in  the  manufacture  of  arsenate  and  arsenite  of  lead, 
we  give  the  following  information  for  the  guidance  of  the  purchaser: 
The  articles  to  be  used  are  acetate  of  lead  (sugar  of  lead)  and  arsenate 
of  soda.  They  should  be  guaranteed  to  be  first  class,  and,  if  necessary, 
the  purchaser  may  have  their  composition  determined  at  the  Experi- 
ment Station. 

First-class  crystallized  lead  acetate  (sugar  of  lead  )  should  contain 
about  58.8  per  cent  of  available  lead  oxid,  but  it  dries  out  or  loses  some 
water  in  the  air  and  thus  ordinarily  contains  from  60  to  62  per  cent.  It 
is  readily  soluble  in  cold  water  in  the  proportion  of  one  pound  to  one 
gallon  of  water.  In  hot  water  it  readily  dissolves  in  a  less  quantity, 
and  for  its  quick  solution  hot  water  is  always  preferable.  This  is  the 
cheapest  water-soluble  lead  salt  in  commerce,  and  therefore  will 
probably  be  used  most  frequently.  Its  wholesale  price  is  7i  cents  per 
pound. 

Arsenate  of  soda  should  have  not  more  than  2  or  3  per  cent  of  chlorin, 
as  this  changes  the  lead  acetate  into  lead  chlorid,  thus  occasioning 
waste;  lead  chlorid  being  of  no  value  as  an  insecticide.  What  is  known 
as  "  sixty-eight  per  cent "  arsenate  of  soda  contains  about  47.8  per  cent 
of  arsenic  acid  and  only  0.57  per  cent  of  chlorin.  The  remainder  of  the 
material  consists  of  the  normal  materials  entering  into  its  composition; 
i.  e.,  soda,  potash,  water  of  crystallization,  a  trifling  amount  of  sulfate 
of  soda,  and  insoluble  matter.  This  salt  is  very  soluble  in  hot  water, 
which  is  preferable  for  its  solution.  The  wholesale  price  of  arsenate 
of  soda  is  5  cents  per  pound. 

The  formula  for  making  one  pound  of  lead  arsenate,  i.  e.,  enough  for 
from  100  to  150  gallons  of  water,  is  to  dissolve  24  ounces  of  acetate  of  lead 
(or  20  ounces  of  lead  nitrate)  in  one  gallon  of  cold  water;  also  separately 
10  ounces  of  arsenate  of  soda  in  three  quarts  of  water;  both  in  wooden 
vessels.  These  weighed  quantities  can  be  bought  in  separate  parcels 
and  are  superior  to  any  mixture  of  them  which  may  be  offered.  The 
separate  solutions  are  to  be  poured  together  into  the  spray  tank  filled 
with  water.  A  white  precipitate  of  lead  arsenate  ready  for  spraying 
immediately  forms  in  the  tank;  its  fine  flocculent  condition  keeps  it  in 
suspension  for  hours,  and  of  all  arsenicals  it  is  the  most  easily  kept 
suspended  in  water. 


ARSENICAL   INSECTICIDES.  29 

The  above  is  the  ordinary  recommendation;  but  the  preparation  can 
be  used  several  times  stronger  if  desired,  without  the  least  danger  of 
producing  any  injury  to  foliage,  even  if  used  at  the  rate  of  from  3  to 
15  pounds  to  100  gallons  of  water. 

To  prove  conclusively  that  this  spray  liquid  contains  lead  in  excess, 
as  it  should,  one  has  only  to  take  out  a  little  of  it  and  test  it  with  a 
few  drops  of  potassium  bichromate,  when  there  should  be  a  yellow- 
colored  precipitate. 

Lead  arsenate,  made  as  above  directed  from  the  best  quality  of  both 
lead  acetate  and  soda  arsenate,  has  the  following  composition: 

Per  Cent. 

Water 2.37 

Leadoxid(PbO)..- 73.10 

Arsenic  pentoxid  (As205) 21.80 

Chlorin 2.40 

Total - - -..- 99.67 

In  the  market  there  are  now  found  several  kinds  of  lead  arsenate 
ready  for  use;  sometimes  it  is  a  dry  powder,  white  or  colored  with  a  dye, 
and  sometimes  a  paste  mixed  with  tar  or  glucose  to  make  it  stick  to  foliage 
or  to  attract  insects.  Such  a  compound  as  the  latter  is  "  Swift's  arsenate 
of  lead."  A  sample  of  the  white  dry  powder  variety  was  shown  by 
analysis  here  to  contain  25.90  per  cent  of  arsenic  pentoxid,  68.06  per 
cent  of  lead  oxid,  and  1.16  per  cent  of  chlorin,  the  rest  being  principally 
water.  There  were  present  0.80  per  cent  of  water-soluble  arsenic 
compounds. 

Swift's  arsenate  of  lead,  in  the  form  of  paste,  usually  has  the  following 
composition,  as  shown  by  an  analysis  recently  made  in  this  laboratory: 

Per  Cent. 

Lead  oxid _. _ 36  00 

Arsenic  pentoxid... 12.00 

Organic  matter  (glucose)  and  other  organic  matter 9.00 

Water 43.00 

Total 100.00 

Water-soluble  arsenic  oxid 0.15 

While  both  of  these  have  the  requisite  amount  of  actual  poison 
to  make  them,  in  practice,  sufficiently  strong  when  made  up  with 
the  usual  quantity  of  water,  they  do  not  come  up  to  the  standard  when 
compared  with  freshly  precipitated,  home-made  lead  arsenate,  for  they 
settle  in  the  spray  tank  much  quicker.  Of  course  the  dry  form  settles 
quickest,  but  remains  in  suspension  about  four  times  as  long  as  the 
finest-powdered  paris  green;  while  the  home-made  lead  arsenate  will 
remain  suspended  fourteen  times  as  long. 

"Disparene"  is  the  trade  name  for  a  much-advertised  new  form  of 
arsenate  of  lead,  a  bluish-gray  colored  paste,  which  the  makers — The 


30  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT   STATION. 

Bowker  Insecticide  Company  of  New  York — describe  as  "a  most  con- 
centrated form  of  arsenical  poison,  put  up  in  the  shape  of  a  dense, 
heavy  white  paste,  which  mixes  well  with  water,  although  it  is  not 
soluble.  Its  complete  insolubility  makes  it  perfectly  safe  to  apply  at 
any  desired  strength  without  burning  or  scorching  the  foliage.  In  this 
and  in  its  great  adhesive  qualities,  lies  its  superiority  to  paris  green  and 
all  other  arsenical  insecticides.', 

"  Disparene  is  used  with  water  at  the  rate  of  two  or  more  pounds  to 
fifty  gallons,  and  retails  for  25  cents  a  pound." 

A  sample  of  this  grayish-blue  paste  has  just  been  received  here,  and 
by  analysis  has  the  following  composition: 

Per  Cent. 

Water  and  volatile  oil 30.5 

Lead  oxid  (PbO)..._ 49.0 

Arsenic  pentoxid  (As205) 16.3 

Tar  and  other  organic  matter. 4.2 

Total .._ _ 100.0 

Water-soluble  arsenic  oxid  . ._ 0.3 

This  material,  as  is  claimed,  is  thus  shown  to  be  a  somewhat  stronger 
poison  than  Swift's,  and  like  it  and  the  Adler  lead  compounds  contains 
very  little  water-soluble  arsenic  compounds.  On  the  average  for  these 
three,  this  matter  amounts  to  only  one  tenth  as  much  as  is  allowable  in 
paris  green.  These  articles,  therefore,  are  perfect  compounds  as  to  free- 
dom from  leaf-burning  ingredients.  But  disparene,  unlike  what  is  said 
of  it  by  its  manufacturers,  will  always  have  this  against  it,  viz.:  that  it 
is  difficult  to  break  up  this  tenacious  paste  and  mix  it  with  water  with- 
out leaving  heavy  lumps  in  the  bottom  of  the  spray  mixture.  Swift's 
lead  poison,  on  the  other  hand,  is  easy  to  work  up  in  water. 

For  the  same  money  that  one  spends  on  such  goods  a  farmer  can 
have  either  arsenate  or  arsenite  of  lead  spray  of  his  own  make  which 
contains  as  much  poison,  and,  moreover,  will  remain  in  suspension  in 
water  nearly  half  again  as  long  a  time. 

Arsenite  of  Lead  is  prepared  by  dissolving  separately  12  ounces  of 
sodium  arsenite  (retailing  at  10  cents  per  pound)  and  4  pounds  of  lead 
acetate  in  water,  then  pouring  them  into  a  150-gallon  spray  tank  filled 
with  water,  when  there  is  obtained  a  milky  mixture  ready  for  spraying 
operations.  Such  a  perfect  mixture  of  di-  and  tri-plumbic  arsenite  will 
remain  in  suspension  nearly  fifteen  times  as  long  as  the  finest-grained 
paris  green.  Another  quality  that  makes  it  of  special  value  is  that  it 
can,  like  lead  arsenate,  be  applied  many  times  stronger  than  recom- 
mended above  without  any  danger  of  scorching  leaves.  The  home-made 
arsenite  of  lead  remains  in  suspension  four  times  as  long  as  does  its 
commercial  relative,  the  "pink  arsenoid,"  mentioned  above. 


ARSENICAL    INSECTICIDES.  31 


Lime  Compounds  of  Arsenic. 


Several  formulas  are  given  for  making  these  sprays,  and  all  yield  the 
same  form  of  poison,  viz.:  calcium  arsenite  (tri-calcic  arsenite),  about 
the  insolubility  of  which  in  water,  when  made  in  the  spray  tank  and 
used  immediately,  there  is  no  dispute.  However,  if  these  compounds 
remain  in  contact  for  long  periods  of  time  (days  and  weeks,  not  hours) 
in  water  they  suffer  a  little  decomposition,  whereby  soluble  arsenites  are 
formed;  and  it  is  certain  that  foliage  can  not  stand  more  of  these  than 
it  can  of  free  "white  arsenic. "  The  several  formulas  for  making  this 
arsenite  (such  as  Taft's,  Kedzie's,  and  Smith's,  although  these  persons 
did  not  invent  them)  are  known,  and  are  given  in  California  Bulletin 
No.  123,  the  supply  of  which  is  unfortunately  nearly  exhausted. 

"Arsenic  and  Lime"  (Taft's  Formula). — Very  satisfactory  directions 
for  making  this  mixture  are  given  in  a  letter  from  Professor  Taft,  of 
Michigan,  one  of  the  first  who  extensively  experimented  with  it;  he 
writes:  "I  have  had  excellent  results  from  boiling  one  pound  of  [white] 
arsenic  and  two  pounds  of  lime  in  two  gallons  of  water  for  forty  minutes 
and  then  diluting  as  required.  When  one  pound  of  the  arsenic  prepared 
as  above,  is  used  in  every  three  hundred  to  four  hundred  gallons  of 
water,  I  have  found  it  equal  to  paris  green  for  destroying  codling-moth 
and  curculio,  while  one  pound  answers  for  one  hundred  and  fifty  to 
two  hundred  gallons  of  water  when  it  is  used  upon  potatoes;  unless 
used  in  Bordeaux  mixture,  I  find  it  best  to  add  a  small  amount  of  lime 
when  diluting.  As  the  wholesale  price  of  arsenic  has  averaged  about 
seven  cents  per  pound  for  a  number  of  years,  while  paris  green  has 
wholesaled  at  eighteen  cents,  it  is  evident  that  the  latter  is  fully  five  times 
as  expensive."  In  reference  to  the  comparative  value  of  arsenic  used 
with  soda  and  lime,  he  further  writes:  "  While  some  recommend  the  use 
of  sal  soda  to  dissolve  the  arsenic,  we  have  not  found  it  necessary;  and 
as  the  use  of  soda  at  the  rate  commonly  recommended  nearly  doubles 
the  expense  of  the  spraying  mixture,  we  have  not  recommended  it, 
although  the  claim  that  when  sal  soda  is  used  it  is  possible  to  tell  when 
the  arsenic  is  dissolved,  is  correct."  The  only  trouble  with  this  mixture 
seems  to  be  the  danger  of  an  incomplete  union  between  the  lime  and  the 
arsenic,  so  that  the  full  forty  minutes'  boiling,  even  with  more  lime  and 
the  addition  of  lime  when  diluting,  would  probably  render  the  mixture 
entirely  safe. 

"Arsenic,  Soda,  and  Lime." — This  is  often  known  as  the  Kedzie 
formula.  The  combination  of  these  three  materials  yields  insoluble 
tri-calcic  arsenite — the  arsenious  oxid  in  the  sodium  arsenite  (formed 
by  dissolving  "white  arsenic"  in  common  sal  soda)  uniting  with  the  cal- 
cium of  the  oxid  of  calcium,  or  lime.    The  reason  for  entering  so  explicitly 


32  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION. 

into  the  description  of  the  action  of  the  components  of  this  formula 
is  that  some  have  tried  to  make  it  with  only  two  of  the  ingredients, 
"white  arsenic "  and  soda;  in  their  haste  they  leave  out  the  vital 
elements  of  the  formula,  the  fresh  lime.  Of  course  their  trees  were 
spoiled,  as  only  arsenate  of  soda  was  formed,  which  burns  the  leaves 
immediately. 

The  method  of  production  is  fully  described  in  the  following  letter 
under  date  of  September,  1899,  from  the  late  Professor  Kedzie,  of  the 
Michigan  Agricultural  College: 

The  formula  I  recommended  for  an  arsenical  spraying  mixture  to  take  the  place  of 
paris  green  was  the  following:  Boil  two  pounds  of  white  arsenic  with  eight  pounds  of 
sal  soda  in  two  gallons  of  rain  water.  Boil  these  materials  together  in  any  iron  pot  not 
used  for  other  purposes ;  boil  them  fifteen  minutes,  or  until  the  arsenic  dissolves,  leaving 
only  a  small  muddy  sediment.  Put  the  solution  in  a  two-gallon  jug  and  label  Poison, 
Stock  material  for  spraying  mixture.  The  spraying  mixture  can  be  prepared  whenever 
required  in  the  quantity  needed  at  the  time,  by  slaking  two  pounds  of  lime,  and  adding 
this  to  forty  gallons  of  water;  pour  into  this  a  pint  of  the  stock  arsenic  solution;  mix 
up,  stirring  thoroughly,  and  the  spraying  mixture  is  ready  for  use.  The  arsenic  in  this 
mixture  is  equivalent  to  four  ounces  of  paris  green. 

Advantages  of  this  Method;  First — It  is  very  cheap  and  the  materials  can  be 
found  in  every  village  in  the  State ; 

Second— The  stock  material  (arsenite  of  soda)  is  easily  prepared  and  can  be  kept  in  that 
form  for  any  length  of  time,  ready  for  making  a  spraying  mixture  of  lime  and  water; 

Third— The  arsenite  of  lime  in  the  quantity  required  for  spraying  will  not  burn  the 
leaves  or  injure  the  trees  or  plants; 

Fourth — It  will  be  uniform  in  quality  and  not  vary  in  strength,  as  paris  green  often 
does; 

Fifth— It  makes  a  milk-colored  spray  and  the  color  on  the  trees  will  show  how  evenly 
it  is  distributed. 

Every  one  using  such  deadly  poison  should  bear  in  mind  the  possible  danger  from  its 
use;  the  pot,  the  jug,  and  every  apparatus  for  making  the  arsenite  of  soda  should  be 
used  for  no  other  purpose  of  any  kind. 

Mr.  Smith,  of  Hood  River,  Oregon,  varies  this  formula,  recommending: 
u Instead  of  two  pounds  of  lime  I  used  not  less  than  six  pounds;  and  I 
found  that  the  additional  lime  prevented  burning  foliage  and  also  retained 
the  poison  longer  on  the  trees.  I  also  used  one  quart  instead  of  one  and 
a  half  pints  of  the  arsenic  to  fifty  gallons  of  water."  And  again," I 
would  recommend  using  freely  of  the  lime  up  to  say  ten  pounds  to  fifty 
gallons  of  water." 

Arsenite  of  calcium  has  been  found  by  us  to  remain  in  suspension 
longer  than  finely  powdered  paris  green  and  somewhat  longer  than  its 
commercial  relative,  london  purple,  which,  when  used  with  fresh  lime, 
probably  becomes  tri-calcic  arsenite,  the  dye  part  of  it  having  no  value 
as  an  insecticide.  Arsenite  of  calcium,  and  even  paris  green  made  up 
with  lime,  has,  when  sprayed  upon  fruit  (apples,  for  instance)  nearly 
ready  for  the  market,  given  the  fruit  a  "whitewashed"  appearance; 
this  is  the  only  complaint  about  it  on  this  side  of  the  subject  which 
has  reached  us.     But  this  is  easy  for  the  farmer  to  avoid. 


ARSENICAL    INSECTICIDES.  33 

DANGER    FROM    THE    USE    OF    ARSENICAL    MIXTURES. 

It  should  be  borne  in  mind  that  arsenic  is  a  very  dangerous  poison 
and  that  in  any  form  it  may  be  fatal  to  man  or  animals;  especially 
should  care  be  taken  in  the  manufacture  of  the  home-made  compounds, 
as  the  handling  necessary  in  these  cases  increases  the  danger  from 
poisoning  through  carelessness.  Properly  handled,  arsenic  is  perfectly 
harmless,  and  there  is  no  excuse  for  any  one  becoming  in  any  way 
affected  by  it.  There  is  in  the  minds  of  a  few  people  some  apprehen- 
sion that  bad  results  might  follow  from  the  use  of  fruit  protected  by 
spraying;  but  this  apprehension  is  certainly  without  foundation.  There 
is  yet  to  be  the  first  case  of  injury  resulting  in  this  way.  In  all 
reported  cases  that  have  come  under  our  observation  the  symptoms 
were  in  no  case  anything  like  those  that  might  be  produced  by  the 
arsenic.  It  is,  nevertheless,  true  that  a  certain  amount  of  arsenic 
remains  on  the  fruit,  and  that  no  one  sprays  any  considerable  time  with 
the  arsenites  without  getting  some  of  the  material  into  the  mouth  or 
lungs;  in  some  cases  even  enough  to  be  recognized  in  the  excretions. 
We  have  known  a  few  cases  in  which  the  person  applying  the  poison 
was  careless  enough  to  become  very  slightly  affected,  the  symptoms 
being  those  of  chronic  arsenic  poisoning.  These  cases  simply  show 
the  need  of  great  care  in  handling  the  poisons,  though  this  can  be  done 
with  perfect  safety  when  care  is  taken. 

SOME    PHYSICAL    PROPERTIES    OF    ARSENICALS. 

All  experimenters  with  arsenicals  agree  with  the  facts  contained  in 
the  following  statements,  and  emphasize  them  in  their  writings. 

One  of  the  most  important  points  in  every  insecticide  applied  with 
water  is  the  time  it  will  remain  in  suspension.  If  the  arsenite  sinks  to 
the  bottom  of  the  spray  tank  in  a  few  minutes,  as  does  paris  green, 
there  is  always  an  unequal  distribution  of  the  poison,  and  the  concen- 
trated mixture  at  the  bottom  is  almost  always  sure  to  "  scorch  "  foliage. 
Generally  speaking,  the  lighter  and  more  flocculent  an  arsenite  is,  the 
longer  it  will  remain  in  suspension  in  the  tank.  So  those  arsenites  of 
high  specific  gravity,  especially  the  dry  powders,  like  paris  green,  Scheele's 
green,  paragrene,  and  dry  lead  preparations  whose  gravities  are  all 
upward  of  3.1  {i.  e.,  higher  than  that  of  quartz  sand  with  2.6  specific 
gravity),  are  objectionable,  because  continuous  stirring  is  required  to 
keep  them  in  suspension.  This  will  always  stand  against  paris  green, 
no  matter  how  pure,  or  how  valuable  an  insecticide  it  may  be. 

In  order  to  bring  out  some  of  the  facts  relating  to  the  power  of  different 
arsenicals  to  remain  in  suspension,  we  have  made  a  series  of  tests  with 
the  different  spray  mixtures,  using  the  same  amount  of  each  poison 
in  each  experiment,  all  at  the  rate  of  1  pound  to  150  gallons  of  water. 
The  following  diagram  shows  the  time,  in  minutes  (the  numerals  after 
each  shaded  column),  that  is  required  for  the  settling  of  each  arsenical 
3 — bull.  151 


34 


UNIVERSITY    OF   CALIFORNIA — EXPERIMENT    STATION. 


through  a  one-foot  column  of  the  water  of  the  practical  spray  mixture. 
The  shaded  columns  show  at  a  glance  the  variations. 


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Here  it  is  readily  seen  that  the  arsenites  and  arsenates  of  lead  easily 
lead  all  other  materials  in  remaining  in  suspension;  and  those  of  this 
group  that  are  capable  of   home-made  production   show   the   greater 


ARSENICAL    INSECTICIDES.  35 

superiority.  As  before  stated,  the  arsenite  of  lead  made  by  pouring 
solutions  of  lead  acetate  and  sodium  arsenite  in  the  filled  tank  rates 
the  highest;  next  comes  the  arsenate  of  lead,  and  both  may  be  roughly 
stated  as  remaining  in  suspension  some  fourteen  or  fifteen  times  longer 
than  the  highest  grade  of  finest  powdered  paris  green,  and  over  fifty 
times  as  long  as  the  coarse-grained  green. 

The  arsenate  of  lead  compounded  with  glucose  (Swift's)  makes  a  fair 
showing  when  compared  with  the  home-made  product,  in  the  proportion 
of  10  to  14  (fine  paris  green  being  the  standard  in  all  cases),  rating 
even  higher  than  the  arsenate  of  lead  made  from  lead  nitrate,  which  is 
found  to  remain  suspended  only  eight  times  longer  than  fine  paris  green. 

When  we  leave  the  home-made  poison  with  lead  base  there  is  seen  to  be 
an  immediate  and  extraordinary  falling  off  in  the  power  of  all  other 
arsenicals  to  remain  in  suspension;  the  arsenite  of  lime  (Kedzie 
formula)  being  only  three  times  better  than  fine  paris  green. 

It  is  interesting  again  to  see  here  how  well  some  manufacturers  of 
arsenical  insecticides  turn  things  to  their  pecuniary  advantage;  witness 
how  easily  the  farmer  is  to  be  imposed  upon  in  the  advice  long  ago 
given  by  careful  experimenters  "  to  color  any  white  powder  around  his 
place  containing  arsenic,  in  order  that  it  may  not  be  mistaken  for  a 
harmless  white  one"; — the  pink  arsenoid,  green  arsenoid,  etc.,  all  give 
in  water  the  various  colors  which  their  names  carry;  and  these  colors  in 
the  liquid  give  the  impression  that  the  poison  remains  long  in  suspen- 
sion, when  in  reality  by  tests  it  has  been  shown  that  the  arsenic  is  at 
the  bottom  of  the  tank.  The  various  dyes,  then,  mask  the  speedy  settling 
of  the  poison,  and  have  been  added  for  that  purpose.  In  none  of  these 
artful  preparations  is  this  property  of  staying  up  in  water  developed  to 
any  particular  extent;  in  any  event,  it  may  be  safely  put  at  only  about 
twice  as  high  as  that  of  first-class  paris  green. 

COST    OF    ARSENICALS. 

It  is  customary  among  writers  on  this  important  point  to  give  state- 
ments showing  simply  the  retail  price  of  different  poisons  to  the  farmer; 
sometimes  the  wholesale  price  is  given.  Besides  these,  two  others,  very 
infrequently  met  with,  can  safely  be  furnished,  viz.:  the  cost  of  the 
arsenical  in  the  various  formulas,  and  also  the  cost  of  these  when  upon 
the  tree. 

Briefly,  from  the  first  point  of  view  the  common  arsenicals  stand  in 
the  following  descending  order  in  prices  per  pound:  paris  green, 
disparene,  paragrene,  Swift's  arsenate  of  lead,  Scheele's  green,  green 
arsenoid,  london  purple,  and,  the  cheapest  of  all,  the  arsenites  of  lime. 
The  rarer  arsenate  and  arsenite  of  lead  are  the  most  expensive  arseni- 
cals used  for  fighting  insect  pests,  but  they  are  said  to  be  applicable  at 
almost  any  strength  without  any  danger  of  burning  foliage. 


36 


UNIVERSITY    OF   CALIFORNIA EXPERIMENT    STATION. 


From  the  second  standpoint,  viz.,  the  cost  of  the  arsenicals  as 
furnished  by  the  different  formulas  for  making  and  applying  them  with 
water,  the  table  below  is  given  to  show  how  they  stand: 

Cost  of  Different  Arsenical  Spraying  Materials. 


Lime, 

® 
1  cent. 

Arsenious 

Oxid  or 

White 

Arsenic, 

@ 
7  cents. 

Sal 

Soda, 

@ 

3  cents. 

Total 

Cost 

per 

rb. 

Gallons. 

Relative 
Strength 

of 
Arsenic 

in 

100 
Gallons. 

0   S 

Oo 

o  ►* 

£° 
2  » 

Paris  Green . 

$0.20 

.70 

1.18 

.29 

.27 
.26 

.71 

150 

640 
400 
400 

150 
150 

150 

750 

914 

339 
1,379 

555 

577 

212 

Ounces. 

Arsenite  of  Lime — 

Kedzie  formula 

Smith  formula 

Taft  formula .. 

$0.32 
.80 
.22 

Arsenate 

and 

Arsenite 

of  Soda, 

@  10  cents. 

$0.06 
.06 

.075 

$0.14 
.14 
.07 

Lead 

Acetate,  or 

Sugar 

of  Lead, 

@  14  cents. 

$0.21 

$0.24 
.24 

Lead 

Nitrate, 

@ 

16 

cents. 

$0^20 

5 
8 
4 

Arsenate  of  Lead— 

From  sugar  of  lead 

From  lead  nitrate 

3% 
5 

Arsenite  of  Lead— 
From  sugar  of  lead 

.63 

Here  it  appears  that  more  gallons  per  dollar  can  be  had  by  the 
arsenite  of  lime  (Taft  formula)  than  by  any  other,  although  the  arsenic 
in  it  per  gallon  is  lower  than  that  in  paris  green,  or  only  4  to  5-J  ounces 
per  100  gallons;  but  all  are  claimed  to  give  equal  satisfaction  as  far  as 
killing  the  codling-moth  is  concerned.  One  dollar  buys,  as  we  see,  only 
one  fourth  as  many  gallons  of  lead  arsenite  as  it  does  of  paris  green  spray. 

When  the  arsenical  is  finally  upon  the  tree — the  last  place  to  consider 
its  cost — it  may  easily  be  seen  from  the  little  table  below  that  after  all 
that  may  be  said  about  the  original  cost  of  arsenicals  and  the  cost  of 
preparing  the  spraying  liquid,  they  amount  to  practically  nothing  when 
the  labor  of  application  to  the  tree  is  considered.  For  the  cost  of 
one  treatment  for  a  tree  of  average  size  (one  gallon  per  tree)  with  the 
different  arsenicals  named,  including  the  cost  of  preparation  of  mixtures 
and  labor  employed  in  applying  them,  is  perhaps  not  far  from  the 
following: 

Cost  of  One  Treatment  with  Different  Kinds  of  Arsenicals. 

Total  Cost 
per  Tree. 

Paris  green  and  lime __.    $0.0563 

London  purple  and  lime 0555 

Arsenates  of  lime — 

Kedzie's .0567 

Swift's -         .0585 

Taft's .0562 

Arsenate  of  lead,  from  sugar  of  lead __.    ...         .0568 

Arsenite  of  lead,  from  sugar  of  lead 


ARSENICAL    INSECTICIDES.  37 

All  of  which  simply  means  that  if  one  can  himself  make  safe 
materials  for  fighting  the  insects  which  destroy  his  crop,  he  has  the 
remedies  not  only  against  them  but  against  the  use  of  impure,  costly 
materials  which  are  frequently  offered  by  the  trade. 

SUMMARY. 

The  results  of  the  examination  of  paris  green  and  other  arsenical 
spraying  materials  may  be  summarized  as  follows: 

First — That  this  market  is  fast  growing  to  be  in  very  fair  condition  as 
to  the  quality  of  the  paris  green  found  in  it;  more  and  more  of  this  poison 
coming  within  the  requirements  of  the  law,  especially  as  regards  those 
containing  less  than  four  per  cent  of  "white  arsenic."  Still  there  is 
much  room  for  improvement  as  compared  with  the  paris  green  on  sale 
in  New  York  State,  where,  according  to  the  reports  of  that  Experiment 
Station,  all  are  satisfactory. 

Second — That  adulteration  in  the  sense  of  adding  foreign  matter, 
"make-weights,"  to  paris  green  (marble  dust,  gypsum,  barium  carbonate, 
etc.)  is  rarely  practiced  in  this  country,  at  least  by  the  manufacturers. 

Third — That  the  examination  of  paris  green,  both  as  regards  the 
physical  and  chemical  tests,  is  not  as  an  obscure  a  matter  as  was 
formerly  claimed  by  some  chemists. 

Fourth — Few  of  the  commercial  substitutes  are  found  to  be  passable 
as  regards  the  water-soluble  arsenic  compounds  in  them;  and  for  this 
reason  and  because  they  possess  little  advantage  over  paris  green  in 
remaining  in  suspension  in  water,  they  are  not  to  be  taken  up  indis- 
criminately by  the  farmer  upon  the  word  of  the  trade. 

Fifth — That  the  insoluble  arsenate  and  arsenite  of  lead  and  arsenite 
of  calcium  (home-made  arsenicals)  are  to  be  recommended  for  extensive 
trial,  especially  the  lead  compounds,  when  heavy  doses  of  poison  are 
required. 

An  Act  to  prevent  fraud  in  the  sale  of  paris  green  used  as  an  insecticide. 

[February  28,  1901,  became  a  law  by  constitutional  limitation.] 

The  People  of  the  State  of  California,  represented   in    Senate   and  Assembly,  do  enact  as 

follows  : 
Section  1.  It  shall  be  the  duty  of  each  and  every  manufacturer  of  paris  green  (com- 
mercial aceto-arsenite  of  copper)  to  be  used  as  an  insecticide  within  this  State,  and  of 
every  dealer  in  original  packages  of  said  paris  green  manufactured  outside  of  this  State, 
before  the  said  paris  green  is  offered  or  exposed  for  sale,  or  sold  within  this  State  as  an 
insecticide,  to  submit  to  the  Director  of  the  California  Agricultural  Experiment  Station 
at  Berkeley,  samples  of  said  paris  green,  and  a  written  or  printed  statement  setting 
forth:  first,  the  brands  of  said  paris  green  to  be  sold,  the  number  of  pounds  contained 
in  each  package  in  which  it  is  put  on  the  market  for  sale,  the  name  or  names  of  the 
manufacturers  and  the  place  of  manufacturing  the  same;  second,  the  statement  shall 
set  forth  the  amount  of  combined  arsenic  which  the  said  paris  green  contains,  and  the 
statement  so  furnished  shall  be  considered  as  constituting  a  guarantee  to  the  purchaser 


38  UNIVERSITY   OF   CALIFORNIA — EXPERIMENT    STATION. 

that  every  package  of  such  paris  green  contains  not  less  than  the  amount  of  combined 
arsenic  set  forth  in  the  statement. 

Sec.  2.  Every  purchaser  of  said  paris  green  in  original  packages,  which  is  manufac- 
tured outside  of  this  State,  who  intends  to  sell  or  expose  the  same  for  sale,  and  every 
manufacturer  of  said  paris  green  within  this  State,  shall,  after  filing  the  statement  above 
provided  for,  with  the  Director  of  the  California  Agricultural  Experiment  Station  at 
Berkeley,  receive  from  the  said  Director  a  certificate  stating  that  he  has  complied  with 
the  foregoing  statement,  which  certificate  shall  be  furnished  without  charge  therefor ; 
said  certificate  when  furnished  shall  authorize  the  party  when  receiving  the  same  to 
deal  in  this  State  in  the  said  paris  green.  Any  person  who  fails  to  comply  with  the 
terms  of  section  one  of  this  Act  shall  not  be  entitled  to  such  certificate  and  shall  not  be 
entitled  to  deal  in  said  paris  green  within  this  State.  Nothing  in  this  section  shall  be 
construed  as  applying  to  retail  dealers  selling  paris  green  which  has  already  been  labeled 
and  guaranteed. 

Sec.  3.  Paris  green,  when  sold,  offered  or  exposed  for  sale,  as  an  insecticide,  in  this 
State,  shall  contain  at  least  fifty  per  centum  of  arsenious  oxid,  and  shall  not  contain 
more  than  four  per  centum  of  the  same  in  the  uncombined  state. 

Sec  4.  The  Director  of  the  California  State  Agricultural  Station  at  Berkeley  shall 
examine  or  cause  to  be  examined  different  brands  of  paris  green  sold,  offered  or  exposed 
for  sale  within  the  State,  and  cause  samples  of  the  same  to  be  analyzed,  and  shall  report 
results  of  analyses  forthwith  to  the  Secretary  of  the  State  Board  of  Horticulture  and  to 
the  party  or  parties  submitting  said  samples,  and  such  report  shall  be  final  as  regards 
its  quality. 

Sec.  5.  Any  person  or  persons,  firm,  association,  company  or  corporation  violating 
any  of  the  provisions  of  this  Act,  and  any  person  who  shall  sell  any  package  of  paris 
green  or  any  part  thereof  which  has  not  been  labeled  as  herein  provided,  shall  be  guilty 
of  a  misdemeanor,  and  shall  be  fined  not  less  than  fifty  dollars  nor  more  than  two  hun- 
dred dollars,  together  with  the  costs  of  the  suit  in  an  action  caused  to  be  brought  by  the 
State  Board  of  Horticulture  through  its  secretary  in  the  name  of  the  people  of  the 
State  of  California. 

Se£.  6.  The  Attorney-General  of  the  State  of  California  is  charged  with  the  prosecu- 
tion of  all  such  suits. 

Sec  7.    This  Act  shall  take  effect  immediately. 

Packages  should  be  sent  to  the  Agricultural  Department  at  Berkeley 
for  examination,  and  growers,  when  purchasing,  should  see  that  a  certifi- 
cate from  the  Director;  Prof.  E.  W.  Hilgard,  accompanies  the  material. 

Dealers  in  paris  green  would  do  well  to  correspond  with  the  Director 
with  regard  to  the  sending  of  samples,  as  the  Station  takes  its  own 
specimens  from  trade  lots  whenever  possible. 


REPORTS  AND  BULLETINS  AVAILABLE  FOR  DISTRIBUTION. 


REPORTS. 


1896.  Report  of  the  Viticultural  Work  during  the  seasons  1887-93,  with  data  regarding 

the  Vintages  of  1894-95. 

1897.  Resistant  Vines,  their  Selection,  Adaptation,  and   Grafting.    Appendix  to  Viti- 

cultural Report  for  1896. 

1898.  Partial  Report  of  Work  of  Agricultural  Experiment  Station  for  the  years  1895-96 

and  1896-97. 
1900.    Report  of  the  Agricultural  Experiment  Station  for  the  year  1897-98. 
1902.    Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

BULLETINS. 

No.  115.  Remedies  for  Insect  and  Fungi.    (Revised.) 

121.  The  Conservation  of  Soil  Moisture  and  Economy  in  the  Use  of  Irrigation  Water. 

125.  Australian  Saltbush. 

127.  Bench-Grafting  Resistant  Vines. 

128.  Nature,  Value,  and  Utilization  of  Alkali  Lands. 

129.  Report  of  the  Condition  of  Olive  Culture  in  California. 

131.  The  Phylloxera  of  the  Vine. 

132.  Feeding  of  Farm  Animals. 

133.  Tolerance  of  Alkali  by  Various  Cultures. 

134.  Report  of  Condition  of  Vineyards  in  Portions  of  Santa  Clara  Valley. 

135.  The  Potato-Worm  in  California. 

136.  Erinose  of  the  Vine. 

137.  Pickling  Ripe  and  Green  Olives. 

138.  Citrus  Fruit  Culture. 

139.  Orange  and  Lemon  Rot. 

140.  Lands  of  the  Colorado  Delta  in  Salton  Basin,  and  Supplement. 

141.  Deciduous  Fruits  at  Paso  Robles. 

142.  Grasshoppers  in  California. 

143.  California  Peach-Tree  Borer. 

144.  The  Peach-Worm. 

145.  The  Red  Spider  of  Citrus  Trees. 

146.  New  Methods  of  Grafting  and  Budding  Vines. 

147.  Culture  Work  of  the  Substations. 

148.  Resistant  Vines  and  their  Hybrids. 

149.  California  Sugar  Industry. 

150.  The  Value  of  Oak  Leaves  for  Forage. 

Copies  may  be  had  by  application  to  the  Director  of  the  Experiment 
Station,  Berkeley,  California. 


